Disc brake and cap seal therefor

ABSTRACT

A disc brake (10) for a motor vehicle comprising a stationary support for mounting on the motor vehicle; a caliper (12) slidably mounted on the stationary support; at least one pin (14) fixed at one end (22) to either the stationary support or the caliper and slidably positioned in an axial bore (16) in the other for slidably mounting the caliper, with the other end (30) of the pin being positioned at or adjacent one end (32) of the axial bore; and a cap seal (36) sealing the one end of the axial bore, the cap seal comprising a base (38) with a continuous wall (40) upstanding from the periphery thereof which is securable to the other of the stationary support or the caliper, and an elastomeric seal (42) secured to the continuous wall for making a seal with the other of the stationary support or the caliper around the one end of the axial bore.

This is a division of application Ser. No. 07/464518 now U.S. Pat. No.5,040,642 filed on Jan. 16, 1990.

This invention relates to a disc brake for a motor vehicle, and to a capseal for the disc brake.

Disc brakes are known which comprise a stationary support for mountingon a motor vehicle, a caliper slidably mounted on the stationarysupport, and at least one pin fixed to either the stationary support orthe caliper and slidably inserted in an axial bore in the other. In sucharrangements, it is known to seal the axial bore at the exposed end ofthe pin with a cap seal in order to prevent dirt and/or moisturereaching the sliding surfaces. However, it has been found that these capseals do not always seal as required. Such a known arrangement is shownin GB Patent No. 1563405.

It is an object of the present invention to provide an arrangement inwhich a more efficient seal is provided

To this end, a disc brake for a motor vehicle in accordance with thepresent invention comprises a stationary support for mounting on themotor vehicle; a caliper slidably mounted on the stationary support; atleast one pin fixed at one end to either the stationary support or thecaliper and slidably positioned in an axial bore in the other forslidably mounting the caliper, with the other end of the pin beingpositioned at or adjacent one end of the axial bore; and a cap sealsealing the said one end of the axial bore, the cap seal comprising abase with a continuous wall upstanding from the periphery thereof whichi of substantially rigid material and which is securable to the saidother of the stationary support or the caliper, and an elastomeric sealsecured to the continuous wall for making a seal with the said other ofthe stationary support or the caliper around the said one end of theaxial bore.

Preferably, the said other of the stationary support or the caliper hasan annularly extending ledge formed therein around the said one end ofthe axial bore, and the continuous wall of the cap seal is resilient andmakes an external push fit with the annularly extending ledge to securethe cap seal. Alternatively, the said other of the stationary support orthe caliper may have a ridge formed therein around the said one end ofthe axial bore, with the continuous wall of the cap seal being resilientand making a snap fit with the ridge to secure the cap seal. As afurther alternative, the said other of the stationary support or thecaliper may have an annularly extending groove formed therein around thesaid one end of the axial bore, with the continuous wall of the cap sealbeing resilient and making an internal push fit with the annularlyextending groove to secure the cap seal.

The elastomeric seal of the cap seal is preferably of rubber and issecured by adhesive to the continuous wall of the cap seal. In thiscase, the elastomeric seal is preferably secured to the free edge of thecontinuous wall.

Alternatively, the elastomeric seal of the cap seal may be of polymericmaterial which is secured by sticking to the continuous wall duringpolymerising of the material. In this case, the elastomeric seal ispreferably secured to the inner surface of the continuous wall.

In the present invention, a substantial improvement in the sealing ofthe cap seal has been found compared to the previously knownarrangements.

The present invention also includes a cap seal for use in a disc brakeas herein described.

The present invention will now be described, by way of example, withreference to the accompanying drawings, in which:

FIG. 1 is a perspective view, partially cut away, of a first embodimentof disc brake in accordance with the present invention;

FIGS. 2A and 2B are alternative cross-sectional views of the cap sealand axial bore in area II of FIG. 1;

FIG. 3 is a top view, partially cut away, of a second embodiment ofbrake caliper in accordance with the present invention; and

FIG. 4 is a top view, partially cut away, of a third embodiment of brakecaliper in accordance with the present invention.

Referring to FIG. 1 of the accompanying drawings, the disc brake 10comprises a caliper 12 which is slidably mountable on a stationarysupport (not shown). The slidable mounting is provide by two pins 14which are spaced apart, and each of which is slidably positioned in anaxial bore 16 in the caliper 12. Each pin 14 is defined by a hollowsleeve 18 of steel and a bolt 20 which passes through the hollow sleeveand is screw threaded at one end 22 to the stationary support. Eachhollow sleeve 18 extends through its respective axial bore 16 and has anouter surface 24 in sliding engagement with the surface 28 of the axialbore. The other end or head 30 of the bolt 20 is positioned in thehollow sleeve 18 at or adjacent one end 32 of the axial bore 16.

At the one end 32 of the axial bore 16, an annularly extending ledge 34is formed in the caliper 12 around the one end 32. A cap seal 36,36'engages the annularly extending ledge 34 to substantially prevent dirtand/or moisture reaching the sliding surfaces 4,28. The cap seal 36,36'is described in more detail with reference to FIGS. 2A and 2B,respectively, in which the bolt 20 has been omitted for clarity. In bothFIGS. 2A and 2B the cap seal 36,36' comprises a base 38 having acontinuous wall 40 upstanding from the periphery of the base andinternal therewith. The base 38 and continuous wall 40 are substantiallyrigid. The material of the continuous wall 40 (which is usually madefrom metallic material) is such that the continuous wall is resilient,and when pushed on to the annularly extending ledge 34, grips theannularly extending ledge to hold the cap seal 36,36' in position. InFIG. 2A, an elastomeric seal 42 of rubber is bonded by a suitableadhesive to a radially outward projecting free edge 44 of the continuouswall 40. On pushing the cap seal 36 on to the annularly extending ledge34, the elastomeric seal 42 engages a radially outward flat 37surrounding the annularly extending ledge to form a seal therewitharound the one end 32 of the axial bore 16. In the alternativearrangement shown in FIG. 2B, an elastomeric seal 42' of polymericmaterial (such as PVC) is defined by a bead 6 which is circumferentiallypositioned around the inner surface 48 of the continuous wall 40. Thebead 46 engages the annularly extending ledge 34 and is captured betweenthe ledge 34 and the continuous wall 40 when the cap seal 36 is pushedinto position to form a seal around the one end 32 of the axial bore 16the ledge 34 isolates the bead 46 from the axial bore 24. The bead 46can be formed by dripping the polymeric material in liquid form onto theinner surface 48 of the continuous wall 40, and then spinning the capseal 36' to spread the liquid. The liquid is such that it sticks andfoams as it dries (polymerises) to form the bead 46.

It has been found that with both of these arrangements the seal aroundthe one end 32 of the axial bore 16 is substantially improved overpreviously known arrangements, with the risk of dirt and/or moisturereaching the sliding surfaces 24,28 through the one end 32 being greatlyreduced.

Further details regarding the operation of the disc brake 10 can beobtained by reference to the above mentioned GB Patent No. 1563405.

In the second embodiment of disc brake 50 shown in FIG. 3, the discbrake comprises a caliper 52 slidably mounted on a stationary support 54by pins 56 and 58. Pin 56 comprises a hollow sleeve 60 with a bolt 62passing through the hollow sleeve and screw threaded to the stationarysupport. The pin 56 is slidably mounted in an axial bore 64 in thecaliper 52. Sealing boots 66 seal each end of the axial bore 64. Bolt 62can be removed to allow the caliper 52 to rotate about the axis 67 ofthe pin 58 relative to the stationary support 54. Pin 58 is in one-pieceand is screw threaded at one end 68 to the stationary support 54 withthe other end 7 of the pin passing through another axial bore 72 in thecaliper 52. The other end 70 of the pin 58 is positioned at or adjacentone end 74 of the axial bore 72, with the outer surface 76 of the pin 58slidingly engaging the inner surface 78 of the axial bore 72. Anannularly extending ledge 80 is formed on the caliper 52 around the oneend 74 of the axial bore 72. A cap seal 82, which is substantiallyidentical to the cap seal 36 shown in FIG. 2A, seals the one end 74 ofthe axial bore 72 to substantially prevent dirt and/or moisture reachingthe sliding surfaces 76,78 through the one end 74.

In the third embodiment of disc brake 90 shown in FIG. 4, like partshave been given the same reference numeral as in FIG. 3. In thisembodiment, the cap seal 92 is substantially identical to the cap seal36' shown in FIG. 2B.

Significant improvements in sealing have been found using thearrangements shown in FIGS. 3 and 4.

Whilst all of the above embodiments disclose cap seals having acontinuous wall which makes an external push fit onto an annularlyextending ledge, several variations of this arrangement could be madewithout departing from the scope of the present invention. For example,the free end of the continuous wall of the cap seal may make a snap fitwith either an outwardly directed ridge or an inwardly directed ridgearound the one end of the axial bore. Alternatively, the continuous wallmay be an internal push fit into an annularly extending groove aroundthe one end of the axial bore.

In all of these alternative arrangements, the elastomeric seal issecured to the continuous wall to seal the one end of the axial bore.Alternative arrangements to those disclosed above include bonding therubber elastomeric seal to the continuous wall in any other suitableposition apart from at the free edge thereof. Further, where thecontinuous wall makes an internal push fit, or a snap fit with aninwardly directed ledge or ridge, the elastomeric seal may be secured tothe outer surface of the continuous wall.

We claim:
 1. A disc brake for a motor vehicle comprising a stationarysupport for mounting on the motor vehicle;a caliper slidably mounted onthe stationary support; at least one pin fixed at one end to either thestationary support or the caliper and slidably positioned in an axialbore in the other for slidably mounting the caliper, with the other endof the pin being positioned adjacent one end of the axial bore whereinthe said other of the stationary support or the caliper has an annularlyextending ledge formed therein around the said one end of the axial borewith a radially outward surrounding flat; a cap seal sealing the saidone end of the axial bore, the cap seal comprising a base with acontinuous wall upstanding from the periphery thereof which is ofsubstantially rigid material and which is securable to the said other ofthe stationary support or the caliper and wherein the continuous wall ofthe cap seal has a radially outward projecting free edge and wherein thecontinuous wall is resilient and makes an external push fit with theannularly extending ledge to secure the cap seal; and an elastomericseal secured to the free edge of the continuous wall for making a sealwith the said other of the stationary support or the caliper around thesaid one end of the axial bore the elastomeric seal being capturedbetween the free edge of the continuous wall and by the flat radiallyoutward from the ledge and the elastomeric seal being isolated from theaxial bore and the pin by the ledge.
 2. A disc brake as claimed in claim1, wherein the elastomeric seal of the cap seal is of polymeric materialwhich is secured by sticking to the continuous wall during polymerisingof the material.
 3. A cap seal for a disc brake for a motor vehicle, thebrake including a stationary support for mounting on the motor vehicle,a caliper slidably mounted on the stationary support, at least one pinfixed at one end to either the stationary support or the caliper andslidably positioned in an axial bore in the other for slidably mountingthe caliper, with the other end of the pin being positioned adjacent oneend of the axial bore wherein the said other of the stationary supportor the claiper has an annularly extending ledge formed therein aroundthe said one end of the axial bore with a radially outward surroundingflat, the cap seal comprising:a base with a continuous wall upstandingfrom the periphery thereof which is of substantially rigid material andwhich is securable to the said other of the stationary support or thecaliper, and wherein the continuous wall of the cap seal has a radiallyoutward projecting free edge and wherein the continuous wall isresilient and makes an external push fit with the annularly extendingledge to secure the cap seal; and an elastomeric seal secured to thefree edge of the continuous wall for making the seal with the said otherof the stationary support or the caliper around the said one end of theaxial bore the elastomeric seal being captured between the freee edge ofthe continuous wall and by the flat radially outward from the ledge andthe elastomeric seal being isolated from the axial bore and the pin bythe ledge.